Portable liquid level detector

ABSTRACT

A portable liquid level detector. The detector comprises a portable casing, a power supply unit disposed in the portable casing, a sensing device coupled to the power supply unit to sense a capacitance within a container and to output a enable signal when a difference in the capacitance is detected, a light emission device coupled to the sensing unit that illuminates after receiving the enable signal, and an alarm device coupled to the sensing unit that sounds after receiving the enable signal.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a portable liquid leveldetector, and method for detecting the level of a liquid in a container.

[0003] 2. Description of the Related Art

[0004] In some semiconductor processes, liquid supply is necessary. Forexample, chemical slurries or the like used in chemical mechanicalpolish (CMP) processes require liquid provision. However, sometimes thecontainer used to contain liquid is nontransparent, so that processengineer doesn't know how much liquid remains in the container. In thiscase, the process engineers sometimes estimate how much liquid remainsin the container by knocking the container and listening to thecorresponding sound from the container. But sometimes the processengineer's estimation is wrong, in which case the liquid supply may beinterrupted, ruining semiconductor products. Another way to know howmuch liquid remains in the container is to use a flow measuring systemto detect the weight of the container with liquid. However, the flowmeasuring system is not cheap. So, if a flow measuring system must beprovided with every process that needs liquid supply, the cost is high.

SUMMARY OF THE INVENTION

[0005] The present invention achieves the above-indicated objects byproviding a portable liquid level detector for determining the level ofthe liquid in the container. According to a first embodiment of thepresent invention, the portable liquid level detector is used to sensewhether a capacitance within a container is changed and to output anenable signal. A light emission device illuminates and an alarm devicesounds after receiving the enable signal, thereby the position of theliquid level in the container is identified.

[0006] According to a second embodiment of the present invention, theportable liquid level detector is used to determine a position of a clogwithin a pipe. A sensor is used to sense whether the clog is jammed inthe pipe and to output an enable signal when the clog is detected by thesensor. A light emission device illuminates and an alarm device sounds,thereby the position of a clog within a pipe is identified.

[0007] The portable liquid level detector has portable casing, a powersupply unit disposed in the portable casing, a sensor coupled to thepower supply unit to sense whether a capacitance within a container ischanged and to output a enable signal when a difference in thecapacitance is detected, a light emission device coupled to the sensorthat illuminates after receiving the enable signal, an alarm devicecoupled to the sensor that sounds after receiving the enable signal, aresistor coupled to the light emission device to limit a current flowingthrough the light emission device, and a switch coupled to the powersupply unit to control an electrical conduction between the power supplyunit and the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The following detailed description, given by way of example andnot intended to limit the invention solely to the embodiment describedherein, will best be understood in conjunction with the accompanyingdrawings in which:

[0009]FIG. 1 shows the portable liquid level detector according to thepresent invention.

[0010]FIGS. 2a˜2 c are schematic diagrams for illustrating the operationof sensor in the portable liquid level detector of the presentinvention.

[0011]FIG. 3 is a schematic diagram for illustrating the operation ofthe first embodiment according to the present invention.

[0012]FIG. 4 is a schematic diagram for illustrating the operation ofthe second embodiment according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] Embodiments of the present invention will be described below withreference to the drawings.

[0014] (First Embodiment)

[0015]FIG. 1 shows a portable liquid level detector according to thepresent invention. The liquid level detector 100 is applied to determinethe liquid level of a container (not shown). The liquid level detector100 includes a portable casing 50 containing a power supply unit 10, asensor 20 coupled to the power supply unit 10 to sense whether acapacitance within a container is changed and to output a enable signalEn1 when the capacitance has changed, a light emission device 30 coupledto the sensor 20 to illuminate after receiving the enable signal En1, analarm device 40 coupled to the sensor 20 to sound after receiving theenable signal En1, a resistor R1 coupled to the light emission device 30to limit a current flowing through the light emission device 30, and aswitch S1 coupled to the power supply unit 10 to control an electricalconduction between the power supply unit 10 and the sensor 20.

[0016] For convenience and portability, the power supply unit 10 ispreferably a battery set. The light emission device 30 is preferably alight emission diode (LED) and the alarm device 40 is preferably abuzzer.

[0017]FIGS. 2a˜2 c are schematic diagrams for illustrating the operationof the sensor 20 in the portable liquid level detector 100 according toa first embodiment of the present invention. For example, the sensor 10is a capacitive proximity switch, E2K-C25ME1 or E2K-C25ME2 made by theOMROM corporation. In FIG. 2a, a capacitive proximity switch 21 contactsa nonmetallic container 22 containing a target liquid 23. At this time,because the capacitive proximity switch 21 is above the position Pb ofthe liquid level, the capacitive proximity switch 21 doesn't detect thetarget liquid 23 in the container 22. Consequently, the capacitiveproximity switch 21 doesn't not output an enable signal En1.

[0018] In FIG. 2b, the capacitive proximity switch 21 is brought intocontact with the nonmetallic container 22 containing the target liquid23, and then is moved downward to the position Pb of the liquid level.The capacitive proximity switch 21 detects a difference in thecapacitance in the container 22, and then the capacitive proximityswitch 21 outputs an enable signal En1. Namely, when the capacitiveproximity switch 21 detects the target liquid 23 in the container 22,the capacitive proximity switch 21 outputs an enable signal En1. Becausethe capacitance above the position Pb is different from capacitancebelow the position Pb, the capacitive proximity switch 21 can detect adifference in the capacitance.

[0019] In FIG. 2c, the capacitive proximity switch 21 is brought intoproximity to but does not contact the metallic container 26 containingthe target liquid 23. If the container 22 is composed of metallicmaterials, the capacitive proximity switch 21 operates by only beingbrought into proximity to the container 26 without contacting container26. Similarly, the capacitive proximity switch 21 does not detect thetarget liquid 23 in the container 26 when the capacitive proximityswitch 21 is above the position Pb of the liquid level. Consequently,the capacitive proximity switch 21 doesn't output an enable signal En1.When the capacitive proximity switch 21 is moved downward to theposition Pb of the liquid level, the capacitive proximity switch 21detects a difference in the capacitance in the container 22, and thenthe capacitive proximity switch 21 outputs an enable signal En1. Namely,whether the containers 22 and 26 are metallic or nonmetallic, once thecapacitive proximity switch 21 moves through the position Pb, thecapacitive proximity switch 21 can detect a difference in thecapacitance. Consequently, the capacitive proximity switch 21 outputsthe enable signal En1. The target 23 can be water, oil, plastics orchemical solutions, or another liquid.

[0020] The operation of the liquid level detector 110 of the presentinvention will be described below in reference to FIG. 1 and FIG. 3.FIG. 1 shows a portable liquid level detector according to the presentinvention and FIG. 3 is a schematic diagram for illustrating theoperation of the first embodiment according to the present invention.

[0021] First, the switch S1 is turned on such that the sensor 20 iselectrically coupled to the power supply unit 10. Further, if thecontainer 111 is composed of nonmetallic materials, the sensor 20 of theliquid level detector 110 is contacted with a container 111 and then theliquid level detector 110 is moved downward or upward. The sensor 20outputs an enable signal En1, when the sensor 20 detects the liquidlevel P1 in the container 111 (a difference in capacitance in thecontainer 111 is detected). The light emission device 30 and alarmdevice 40 are coupled to the sensor 20. The light emission device 30illuminates and the alarm device 40 sounds after receiving the enablesignal En1, such that the liquid level of the container 111 isidentified.

[0022] Furthermore, if the container 111 is composed of metallicmaterials, the sensor is moved into proximity to the container 111without contacting it. Then the liquid level detector 110 is moveddownward or upward. The sensor 20 outputs an enable signal En1, when thesensor 20 detects the liquid level PI in the container 111. The lightemission device 30 illuminates and the alarm device 40 sounds afterreceiving the enable signal En1, such that the liquid level of thecontainer 111 is identified.

[0023] (Second Embodiment)

[0024] The operation of the liquid level detector 110 according to thesecond embodiment of the present invention will be described below inreference to FIG. 1 and FIG. 4. FIG. 1 shows a portable liquid leveldetector according to the present invention and FIG. 4 is a schematicdiagram for illustrating the operation of the second embodiment todetect a clog or jam in a pipe.

[0025] In FIG. 4, a clog 250 is jammed in a non-transparent pipe 210. Ifthe container pipe 210 is composed of metallic materials, the sensor 20of the liquid level detector 110 is moved into proximity to the pipe 210without contacting it. Then the liquid level detector 110 is moved toposition P3 from position P2 or to position P4 from position P5 alongthe pipe 210. The sensor 20 outputs an enable signal En1, when thesensor 20 detects the clog 250 in the pipe 210 (a difference in thecapacitance in pipe 210 is detected). The light emission device 30 andalarm device 40 are coupled to the sensor 20. The light emission device30 illuminates and the alarm device 40 sounds after receiving the enablesignal En1, such that the location of the clog 250 in the pipe 210 isidentified.

[0026] If the container 111 is composed of nonmetallic materials, thesensor 20 of the liquid level detector 110 is brought into contact thepipe 210. Then the liquid level detector 110 is moved to position P3from position P2 or to position P4 from position P5 along the pipe 210.The sensor 20 outputs an enable signal En1, when the sensor 20 detectsthe clog 250 in the pipe 210 (a difference in the capacitance in pipe210 is detected). The light emission device 30 and alarm device 40 arecoupled to the sensor 20. The light emission device 30 illuminates andthe alarm device 40 sounds after receiving the enable signal En1, suchthat the location of the clog 250 in the pipe 210 is identified.

[0027] The portable level detector of the present invention isconvenient and cheap. The present invention uses a capacitive proximityswitch to detect capacitance variation, and then outputs an enable sothat a LED illuminates and a buzzer sounds, thereby identifying a liquidlevel position in a container.

[0028] Moreover, the portable level detector can also be used to detectthe location of the clog in a nontransparent pipe. Wherever, theportable level detector can detect the level of the liquid in a metallicmaterials or a nonmetallic container.

[0029] Finally, while the invention has been described by way of exampleand in terms of the preferred embodiment, it is to be understood thatthe invention is not limited to the disclosed embodiments. On thecontrary, it is intended to cover various modifications and similararrangements as would be apparent to those skilled in the art.Therefore, the scope of the appended claims should be accorded thebroadest interpretation so as to encompass all such modifications andsimilar arrangements.

What is claimed is:
 1. A portable liquid level detector, comprising: aportable casing; a power supply unit disposed in the casing; a sensorcoupled to the power supply unit to sense whether a capacitance within acontainer is changed and to output a enable signal when the capacitancehas changed; and a signal device coupled to the sensor that outputs asignal after receiving the enable signal.
 2. A portable liquid leveldetector as claimed in claim 1, wherein the signal device is an alarmdevice.
 3. A portable liquid level detector as claimed in claim 1,wherein the signal device is a light emission device.
 4. A portableliquid level detector as claimed in claim 3, further comprising aresistor coupled to the light emission device to limit a current flowingthrough the light emission device.
 5. A portable liquid level detectoras claimed in claim 3, wherein the light emission device is a lightemission diode.
 6. A portable liquid level detector as claimed in claim2, wherein the alarm device is a buzzer.
 7. A portable liquid leveldetector as claimed in claim 1, wherein the sensor is a capacitiveproximity switch.
 8. A portable liquid level detector as claimed inclaim 1, wherein the power supply unit is a battery set.
 9. A portableliquid level detector as claimed in claim 1, further comprising a switchcoupled to the power supply unit to control the electrical conductionbetween the power supply unit and the sensor.
 10. A portable liquidlevel detector, comprise: a portable casing; a battery set deposed inthe portable casing; a capacitive proximity switch coupled to thebattery set to sense whether a capacitance within a container is changedand to output a enable signal when the capacitance has changed; a lightemission diode coupled to the capacitive proximity switch thatilluminates after receiving the enable signal; a buzzer coupled to thecapacitive proximity switch that sounds after receiving the enablesignal; a resistor coupled to the light emission diode to limit acurrent flowing through the light emission diode; and a switch coupledto the battery set to control a electrical conduction between thebattery set and the capacitive proximity switch.
 11. A method ofdetecting liquid level in a container, comprising: moving a capacitiveproximity switch into proximity of a container contains a liquid; andmoving the capacitive proximity switch upward and downward relative tothe container until a difference in capacitance is detected.
 12. Themethod as claimed in claim 11 wherein the container is nonmetallic, andthe step of moving the capacitive proximity switch into proximity of thecontainer brings the capacitive proximity switch into contact with thecontainer.
 13. The method as claimed in claim 11 wherein the containeris metallic, and the step of moving the capacitive proximity switch intoproximity of the container brings the capacitive proximity switch closeto but not contact with the container.
 14. A method of detecting a clogjammed in a pipe, comprising: moving a capacitive proximity switch intoproximity of a pipe with a clog; and moving the capacitive proximityswitch upward and downward relative to the pipe until a difference incapacitance is detected.
 15. The method as claimed in claim 14 whereinthe container is nonmetallic, and the step of moving the capacitiveproximity switch into proximity of the pipe brings the capacitiveproximity switch into contact with the pipe.
 16. The method as claimedin claim 14 wherein the container is nonmetallic, and the step of movingthe capacitive proximity switch into proximity of the pipe brings thecapacitive proximity switch close to but not in contact with the pipe.